Abstract

A6

Background: Metastatic breast cancer (MBC) is an incurable condition treated with palliative intent. The detection of CTCs at baseline and during therapy is an independent strong prognostic marker and is predictive of treatment outcome. We compared the CellSearch Assay with the AdnaTest Breast Cancer to evaluate sensitivity in detection of CTCs in patients with MBC.Material and Methods: This was a prospective study including 74 patients with MBC evaluated at the University of Texas, M D Anderson Cancer Center. CTCs from 7.5 mL of whole blood were isolated and enumerated using the CellSearch assay (Veridex, LLC, Warren, NJ), before patients started a new treatment. CTCs were considered negative (-) or positive (+) if <5 and >5 respectively. ) The AdnaTest Breast Cancer uses 5ml of whole blood for magnetically coupled antibodies directed to multiple cell surface antigens to capture the CTCs, followed by multiplexed RT-PCR for tumor markers (GA733.2, MUC-1 and Her-2) for CTC detection. CTC (+) was defined by the detection of one or more of the 3 markers. The chosen cut-off value for positivity was 0.15 ng/μL. The primary purpose of this study was to determine whether the AdnaTest Breast Cancer results (individual components or whole) correspond to CellSearch low or high (>= 5) CTCs. Results: Median age at MBC diagnosis was 56 years. Hormone receptor status was positive in 69% of patients. Her-2 positive (FISH amplification) was demonstrated in 18 patients (24%). Twenty-six patients (35%) were CTCs (+) by the CellSearch technology, while 33 pts (44%) were CTCs (+) by the AdnaTest Breast Cancer. The individual markers positivity was: 13% GA733.2, 35% MUC-1, 30%. Her-2 There was an overall positive agreement of 55% and a negative percent agreement of 69.5% between the 2 technologies. Neither technology was found to be related to either ER/PR or Her-2 status of primary tumor. Moreover sixteen pts with Her-2 positive CTCs had no evidence of Her-2 amplification in the primary tumor. Conclusion: This preliminary data indicate that the AdnaTest Breast Cancer may represent a more sensitive technique for detection of CTCs in patients with MBC. Larger prospective confirmatory studies are planned.